135 lines
3.7 KiB
C++
135 lines
3.7 KiB
C++
/*
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* pg_test_timing.c
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* tests overhead of timing calls and their monotonicity: that
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* they always move forward
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*/
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#include "postgres_fe.h"
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#include "getopt_long.h"
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#include "portability/instr_time.h"
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static const char* progname;
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static int32 test_duration = 3;
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static void handle_args(int argc, char* argv[]);
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static void test_timing(int32);
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int main(int argc, char* argv[])
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{
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progname = get_progname(argv[0]);
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handle_args(argc, argv);
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test_timing(test_duration);
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return 0;
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}
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static void handle_args(int argc, char* argv[])
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{
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static struct option long_options[] = {{"duration", required_argument, NULL, 'd'}, {NULL, 0, NULL, 0}};
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int option; /* Command line option */
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int optindex = 0; /* used by getopt_long */
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if (argc > 1) {
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if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0 || strcmp(argv[1], "-?") == 0) {
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printf("Usage: %s [-d DURATION]\n", progname);
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exit(0);
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}
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if (strcmp(argv[1], "--version") == 0 || strcmp(argv[1], "-V") == 0) {
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puts("pg_test_timing (PostgreSQL) " PG_VERSION);
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exit(0);
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}
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}
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while ((option = getopt_long(argc, argv, "d:", long_options, &optindex)) != -1) {
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switch (option) {
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case 'd':
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test_duration = atoi(optarg);
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break;
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default:
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fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
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exit(1);
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break;
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}
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}
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if (argc > optind) {
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fprintf(stderr, "%s: too many command-line arguments (first is \"%s\")\n", progname, argv[optind]);
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fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
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exit(1);
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}
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if (test_duration > 0) {
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printf("Testing timing overhead for %d seconds.\n", test_duration);
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} else {
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fprintf(stderr, "%s: duration must be a positive integer (duration is \"%d\")\n", progname, test_duration);
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fprintf(stderr, "Try \"%s --help\" for more information.\n", progname);
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exit(1);
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}
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}
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static void test_timing(int32 duration)
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{
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uint64 total_time;
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int64 time_elapsed = 0;
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uint64 loop_count = 0;
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uint64 prev, cur;
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int32 diff, i, bits, found;
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instr_time start_time, end_time, temp;
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static int64 histogram[32];
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char buf[100];
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total_time = duration > 0 ? duration * 1000000 : 0;
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INSTR_TIME_SET_CURRENT(start_time);
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cur = INSTR_TIME_GET_MICROSEC(start_time);
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while (time_elapsed < total_time) {
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prev = cur;
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INSTR_TIME_SET_CURRENT(temp);
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cur = INSTR_TIME_GET_MICROSEC(temp);
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diff = cur - prev;
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if (diff < 0) {
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printf("Detected clock going backwards in time.\n");
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printf("Time warp: %d microseconds\n", diff);
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exit(1);
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}
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bits = 0;
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while (diff) {
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diff >>= 1;
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bits++;
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}
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histogram[bits]++;
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loop_count++;
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INSTR_TIME_SUBTRACT(temp, start_time);
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time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
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}
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INSTR_TIME_SET_CURRENT(end_time);
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INSTR_TIME_SUBTRACT(end_time, start_time);
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printf("Per loop time including overhead: %0.2f nsec\n", INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
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printf("Histogram of timing durations:\n");
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printf("%9s: %10s %9s\n", "< usec", "count", "percent");
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found = 0;
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for (i = 31; i >= 0; i--) {
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if (found || histogram[i]) {
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found = 1;
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/* lame hack to work around INT64_FORMAT deficiencies */
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snprintf(buf, sizeof(buf), INT64_FORMAT, histogram[i]);
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printf("%9ld: %10s %8.5f%%\n", 1l << i, buf, (double)histogram[i] * 100 / loop_count);
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}
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}
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}
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